1. Field of the Invention
The present invention concerns an extensible chain particularly suitable for making an ornamental item to be worn, like for example a bracelet, a necklace or similar objects.
The present invention also concerns an ornamental item comprising the above mentioned extensible chain.
2. Present State of the Art
As is known, there are various types of necklaces, bracelets and other analogous ornamental objects comprising a plurality of elements connected to one another in succession to form a chain.
According to one of said known embodiments, the chain comprises a plurality of cage-shaped elements connected in succession, each one of which is constituted by a central body from which two or more lateral bodies branch off whose free ends face the corresponding central body and are arranged opposite each other and inserted in an adjacent cage-shaped element.
The lateral bodies delimit the cage-shaped element laterally and are spaced from each other in such a way as to define slits that slidingly house the free ends of an adjacent cage-shaped element.
The chain described above is deformable and extensible in such a way as to adapt to the wrist, neck or even finger (in the case of a ring) of the person who wears it, since each cage-shaped element can slide in the adjacent cage-shaped element and can also assume various inclinations with respect to it.
Said chain is particularly simple to construct, since it comprises a single type of modular element that can be connected to other analogous elements in any number in order to make chains having various lengths.
An example of a chain made according to the technique explained above is described in the European Patent EP 1 943 916 B1, in the name of the same applicant that is filing the present invention.
The chain just mentioned above comprises cage-shaped elements, each one of which has its two ends that penetrate the ends of corresponding adjacent elements.
In this way, the ends of two adjacent elements delimit an intermediate space in which a cylindrical spring is interposed.
As the elements are arranged in such a way as to penetrate each other, when the chain is stretched the ends of the elements of each pair move near each other and compress the springs.
When the chain is released, the elastic reaction generated by the springs tends to make the chain return to the rest position.
Notwithstanding the advantages deriving from the above mentioned elasticity, the maximum stretching is limited by the length of the springs in the configuration of maximum compression, substantially corresponding to the number of turns multiplied by the thickness of the material of which they are made.
For the purpose of increasing the elasticity of the chain, that is, of increasing the difference in length between the rest position and the maximum extension of the chain, the Patent application VI2009A000236 describes the use of a spring that is not cylindrical any longer but in the shape of a truncated cone, so that during the compression stage the turns are arranged on the same plane and thus the overall dimensions of the compressed spring correspond to the diameter of a turn.
This solution, which seemed to be suited to solve the problem of increasing the elasticity of the chain, has proven to be unfeasible due both to the high cost of the equipment necessary to make a truncated cone-shaped spring with the reduced dimensions typical of the springs used in jewellery and to the fact that the presence of the helical shape leads to problems related to the need to center the spring with respect to the elements between which it is included and to keep it in position while the chain is being used by the users.